Vitamin D Update

THE BASICS: Vitamin D has been getting considerable attention for its important role in maintaining strong bones and reducing the long-term risk of cancer. But it has many other health benefits, such as reducing back pain, the risk of developing Alzheimer's and related diseases, and susceptibility to colds and the flu.

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ALIAS: The two most common forms are vitamin D3 (cholecalciferol) and D2 (ergocalciferol). Vitamin D3 is preferred; D2 has only about half the potency.

HOW VITAMIN D WORKS: We make our own vitamin D when our skin is exposed to sunlight. Ultraviolet rays in sunlight initiate a series of chemical reactions that convert cholesterol in the skin to vitamin D, and the vitamin is subsequently turned into the hormone calcitriol. However, when we use sunscreen outdoors or spend most of our time indoors, we block this natural means of making this vitamin.

HEALTH BENEFITS: Over the past several years, research has revealed multifaceted benefits of vitamin D. Here's an overview:

Bone and muscle. You need vitamin D to make both bone and muscle. Doctors used to believe that weak bones led to falls and fractures, but current medical thinking is that weak muscles lead to falls and broken bones. Several studies have found that supplementation with vitamin D reduces the likelihood of falls.

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Aches and pains. In a study of more than 3,000 men, low vitamin D levels were associated with a 50 percent higher chance of suffering from "chronic widespread pain." A separate study found that low vitamin D doubled the risk of chronic back pain in women. Meanwhile, a report in The Journal of the American Board of Family Medicine described six patients who had experienced severe back pain, two of whom who had undergone back surgery. All of the patients improved after taking 1,000 to 5,000 IU of vitamin D daily for at least three to six weeks.

WHAT THE LATEST GUIDELINES MEAN

Confused about the relatively low vitamin D recommendations from the National Institute of Medicine? The vitamin D committee focused strictly on bone health, and did not include any experts on vitamin D. The committee's recommendation to take 600 IU of vitamin D daily is probably sufficient to maintain strong bones; however, if you want to reduce your risk of cancer, heart disease, diabetes, depression, pain, and colds and flus, you would most likely do better taking at least 1,000 to 2,000 IU of vitamin D each day, maybe more.

Mental and neurological health. Two new studies suggest that low levels of vitamin D may contribute to cognitive decline and Parkinson's disease and, conversely, that high levels of the vitamin may be protective. In the first study, researchers tested 858 seniors; those deficient in vitamin D were 60 percent more likely to suffer from cognitive decline during the six-year study. A 30-year study in Finland found that high levels of vitamin D appeared to reduce the risk of Parkinson's disease by two-thirds.

Flu protection. A study of Japanese children found that vitamin D supplements reduced the risk of contracting the flu by 42 percent. The children also had an 83 percent lower risk of asthma attacks.

Blood sugar. An analysis of 28 studies found that people with high blood levels of vitamin D have a low risk of developing cardio-metabolic diseases, including cardiovascular disease, type 2 diabetes, and metabolic syndrome. Another study demonstrated that vitamin D and calcium supplements prevented increases in fasting blood sugar, while blood sugar levels increased substantially among people given placebos.

BACKGROUND CHECK: Vitamin D is safe. You would have to take 50,000 IU daily for several months to develop toxicity.

GLEANINGS: Three of every four Americans do not have optimal levels of vitamin D, according to a study in the Archives of Internal Medicine.

HEADS UP: Researchers at the Medical University of Graz, Austria, found that people with low blood levels of vitamin D were twice as likely to die from any cause, compared with people who had high levels of the vitamin.

WHAT SHOULD YOU TAKE: If you stand in the summer sun (in a T-shirt and walking shorts and without sunscreen) for about 10 minutes, your body will produce about 10,000 IU of vitamin D. Alternatively, take 1,000 to 2,000 IU daily, doubling that amount if you have a dark complexion.